1. Field of the Invention
This invention pertains to closed cycle hot gas engines operating on the Ericsson Cycle. The working as is operated on inside heat regenerator and a heat addition means equipped cylinder. Transfer of the working gas into and out of the active engine components is accomplished by a piston reciprocating inside the cylinder and piston position synchronized valves.
2. Description of the Prior Art
Extensive developmental work on hot gas engines, primarily of the Stirling type, is currently being carried out in several countries. In Stirling Engines, the working gas is transferred between a cold and a hot cylinder containing a moving piston, the transfer taking place via a heat regenerator and a heater. Thermal net efficiencies (mechanical net power output divided by total applied chemical heat input) near 40% for stationary operating conditions have been demonstrated experimentally with such engines, and temperatures of around 750.degree. C. have been used in the heater.
The problems associated with Stirling engines are numerous, however, Among them are problems with materials, manufacturing problems, and mechanization problems. In a majority of the hot gas engine mechanisms, the working gas does not follow the high thermal efficiency Stirling or Ericsson cycle loops. This is because of he presence of working as in the cold cylinder or the crossing over of working gas from the hot cylinder to the cold cylinder during the expansion step, and the presence of working gas in the hot cylinder during the compression step. These conditions make the working gas processing steps not ideal for optimum heat regeneration.
The finite volume of the heat regenerator is one impediment to making all the working gas (taking part in an engine cycle) follow the same Stirling or Ericsson cycle loop. However, the mechanisms in U.S. Pat. No. 4,327,550 and 4,455,825 enable each elemental quantity of working gas to follow an elemental Ericsson cycle loop. The specific elemental Ericsson cycle loop performed by a given elemental quantity of working gas depends upon its position in the heat regenerator. The nearer the elemental quantity of working gas is to the hot end of the heat regenerator, the closer the elemental Ericsson cycle loop is to the isotherm coresponding to the hot end of the regenerator. The elemental Ericsson cycle loops consist of heat additions from the regenerator material or heat addition means in the cylinder at the higher temperature isotherm during the expansion step, and heat rejections to the heat regenerator material during the compression step. When the elemental Ericsson Cycle loops for all the elemental quantities of working gas are integrated we get the overall Ericsson cycle loop which consists of heat addition at the temperature coresponding to the hot end of the regenerator or the hot cylinder and heat rejection at the temperature coresponding to the cold end of the heat regenerator or the cold cylinder.
The feature that makes the integrated Ericsson cycle loop possible in the two patents mentioned above, is the plug flow movement of the working gas towards the hotter region of the system followed by the expansion step during which each elemental quantity of working gas in the system is moved towards a hotter region of the system, followed by a plug flow movement of the working gas in the system towards the colder regions of the system followed by the compression step during which each elemental quantity of the working gas is moved towards the colder regions of the system. By plug flow is meant that each elemental quantity of working gas maintains its longitudinal relationship in the system with all other elemental quantities of working gas within the system for the duration of the plug flow, the longitudinal axis being in the direction of the flow. The present invention mechanism solves the heat regeneration problem in a similar way to the above reference U.S. Pat. Nos., except it uses only one cylinder instead of a pair of cylinders.